Stuck on an issue?

Informations

what i need to do is to append html elements and text such as :

var bold = document.createElement("b");
var italic = document.createElement("i");
var underline = document.createElement("u");
var text= document.createTextNode("hi");
 italic.appendChild(bold);
 bold.appendChild(text);
 underline.appendChild(italic); 

now i have to insert it into editor.

I am making smth for transcribing, so this would be used on key cmd to insert some kind of text.

for inserting regular text, without style, I used this function

// adds  Speaker's id into the editor
function addSpeaker(savedID){ 
  if(savedID==null){
    return;
  } else{
    var x = document.execCommand('insertHTML', false, savedID);
    console.log(byId('editor'));
    console.log(x);
  }
}

I tried

// Set HTML content
trumbowyg.html('<p>Your content here</p>');

all the possibilities, but none of them works.

help?